JMock-A Slightly Bigger Example

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Introduction

This is a complete, albeit simple, example using jMock. To get this running, you'll need to do the following

1. Use Java 5 or later
2. Add JUnit 4 to your classpath
3. Download jMock
4. Extract the download and add the 4 jars into your classpath (note your version numbers might be different):
   • jmock-2.0.0.jar
   • jmock-junit4-2.0.0.jar
   • hamcrest-api-1.0.jar
   • hamcrest-library-1.0.jar
5. Take each of the following files and add them into a project in your favorite IDE

WithdrawalTest.java

package com.objectmentor.jmock;
 
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import junit.framework.JUnit4TestAdapter;
 
import org.jmock.Expectations;
import org.jmock.Mockery;
import org.jmock.integration.junit4.JMock;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
 
@RunWith(JMock.class)
public class WithdrawalTest {
    public static junit.framework.Test suite() {
        return new JUnit4TestAdapter(WithdrawalTest.class);
    }
 
    Withdrawal withdrawal;
    Mockery context = new Mockery();
 
    BankAccount account;
 
    @Before
    public void initialize() {
        withdrawal = new Withdrawal();
        withdrawal.setAmount(1500);
        account = context.mock(BankAccount.class);
        withdrawal.setAccount(account);
    }
 
    @Test
    public void failExecutionIfBalanceInadequate() {
        context.checking(new Expectations() {
            {
                one(account).getBalance();
                will(returnValue(1000));
            }
        });
 
        boolean exceptionThrown = false;
 
        try {
            withdrawal.execute();
        } catch (InsufficientFunds e) {
            // success
            exceptionThrown = true;
        }
        assertTrue("Should have thrown: " + InsufficientFunds.class,
                exceptionThrown);
    }
 
    @Test
    public void executeWithdrawChangesBalanceAndSetsExecuted() {
        context.checking(new Expectations() {
            {
                ignoring(account).getBalance();
                will(returnValue(2500));
                one(account).deduct(with(equal(1500)));
            }
        });
 
        withdrawal.execute();
 
        assertEquals(true, withdrawal.isExecuted());
    }
 
    @Test
    public void methodThatWeExpectWillThrowAnException() {
        boolean expectedThrown = false;
 
        try {
            throw new RuntimeException();
        } catch (RuntimeException e) {
            expectedThrown = true;
        }
 
        assertTrue(expectedThrown);
    }
}

BankAccount.java

package com.objectmentor.jmock;
 
public interface BankAccount {
    int getBalance();
    void deduct(int i);
}

Withdrawal.java

package com.objectmentor.jmock;
 
public class Withdrawal {
    private BankAccount account;
    private int amount;
    public boolean executed;
 
    public void setAmount(int amount) {
        this.amount = amount;
    }
 
    public void setAccount(BankAccount account) {
        this.account = account;
    }
 
    public void execute() {
        if (account.getBalance() < amount) {
            throw new InsufficientFunds();
        }
        account.deduct(amount);
        executed = true;
    }
 
    public boolean isExecuted() {
        return executed;
    }
}

InsufficientFunds.java

package com.objectmentor.jmock;
 
public class InsufficientFunds extends RuntimeException {
    private static final long serialVersionUID = 1L;
}

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